Hurricane FELICIA (Text)

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HURRICANE FELICIA DISCUSSION NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP082009
800 PM PDT FRI AUG 07 2009
SATELLITE IMAGERY...INCLUDING A TRMM OVERPASS...INDICATE THAT
FELICIA HAS BECOME BETTER ORGANIZED DURING THE PAST SEVERAL HOURS.
THE EYE IS MORE DISTINCT...AND THE EYEWALL IS MORE SYMMETRIC WITH
COLDER CLOUD TOPS. SATELLITE INTENSITY ESTIMATES ARE 102 KT FROM
TAFB AND 90 KT FROM SAB. BASED ON THIS...THE INITIAL INTENSITY IS
INCREASED TO 90 KT...AND THIS COULD BE A LITTLE CONSERVATIVE. THE
HURRICANE REMAINS IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT WITH
GOOD CIRRUS OUTFLOW OVER THE WESTERN SEMICIRCLE AND FAIR OUTFLOW
ELSEWHERE.
THE INITIAL MOTION IS 295/12. WATER VAPOR IMAGERY AND LARGE-SCALE
MODEL ANALYSES SUGGEST THAT THE SUBTROPICAL RIDGE IS BUILDING NORTH
OF FELICIA...WHICH SHOULD CAUSE THE HURRICANE TO TURN GRADUALLY
WESTWARD DURING THE NEXT 24-36 HR. AFTER THAT...THE MODELS
FORECAST FELICIA TO ENCOUNTER INCREASING UPPER-LEVEL WESTERLIES...
A BREAK IN THE MID-LEVEL RIDGE EAST OF THE HAWAIIAN ISLANDS...AND A
WEAK MID-LEVEL ANTICYCLONE FORMING JUST SOUTHWEST OF THE ISLANDS.
THE MODELS SHOW THIS EVOLUTION BLOCKING THE WESTWARD MOTION OF THE
MID- AND UPPER-LEVEL PORTIONS OF FELICIA...CAUSING THE STORM TO
SHEAR APART IN ABOUT 48 HR. THE WEAKENING LOW-LEVEL CIRCULATION
WOULD THEN CONTINUE WESTWARD IN THE TRADE WINDS. ALL MODEL GUIDANCE
AGREES WITH THIS SCENARIO...AND THE OFFICIAL FORECAST FOLLOWS
IT...CALLING FOR FELICIA TO PASS NEAR THE ISLAND OF HAWAII BETWEEN
72-96 HR. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS
FORECAST AND LIES JUST SOUTH OF THE MODEL CONSENSUS. AN
ALTERNATIVE SCENARIO IS FOR FELICIA TO MAINTAIN SOME VERTICAL
INTEGRITY AND BE STEERED TOWARD THE WEST-SOUTHWEST BY THE MID-LEVEL
RIDGE NEAR HAWAII.
FELICIA IS STILL MOVING OVER COOLING SEA SURFACE TEMPERATURES...AND
SHOULD CONTINUE TO DO SO FOR ANOTHER 12-18 HR. THIS SHOULD CAUSE
THE HURRICANE TO WEAKEN...THE RECENT INTENSIFICATION
NOTWITHSTANDING. WHILE THE SSTS ALONG THE FORECAST INCREASE
STARTING IN ABOUT 24 HR...THE CYCLONE IS LIKELY TO CONTINUE
WEAKENING DUE TO THE INCREASED SHEAR BEGINNING IN 36-48 HR. ALL
INTENSITY GUIDANCE CALLS FOR WEAKENING AS FELICIA APPROACHES
HAWAII...AND THE NEW INTENSITY FORECAST FOLLOWS THE GUIDANCE IN
BEST AGREEMENT WITH THE INTENSITY CONSENSUS MODEL. IF FELICIA
MOVES SOUTH OF THE FORECAST TRACK...IT WOULD ENCOUNTER WARMER SSTS
AND LESS SHEAR...WHICH COULD ALLOW IT TO REMAIN STRONGER THAN
FORECAST. ON THE OTHER HAND...ANY MOTION NORTH OF THE FORECAST
TRACK WOULD STEER THE CYCLONE INTO STRONG SHEAR NORTH OF HAWAII AND
HASTEN ITS DEMISE.
FORECAST POSITIONS AND MAX WINDS
INITIAL 08/0300Z 18.8N 138.0W 90 KT
12HR VT 08/1200Z 19.3N 139.8W 80 KT
24HR VT 09/0000Z 19.5N 142.4W 70 KT
36HR VT 09/1200Z 19.6N 145.0W 65 KT
48HR VT 10/0000Z 19.6N 147.6W 55 KT
72HR VT 11/0000Z 19.5N 153.0W 35 KT
96HR VT 12/0000Z 19.5N 159.0W 30 KT
120HR VT 13/0000Z 20.0N 164.0W 20 KT...REMNANT LOW
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FORECASTER BEVEN
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